Telegraph receiving system



Feb. 10, 1931. F. J. SINGER 1,791,578

TELEGRAPH RECEIVING SYSTEM Filed March 20. 1929 Band Filter INVENTOR EJJIL/ er ATTORNEY Patented Feb. 10, 1931 UNITED STATES PATENT OFFICE FRED J. 'SINGER, OF ROCKVILLE CENTER, NEW YORK, ASSIGNOR TO AMERICAN TELE- PHONE AND TELEGRAPH COMPANY, A. CORPORATION OF NEW YORK TELEGRAPH RECEIVING SYSTEM Application filed March 20,

This invention relates to signalingsystems and particularly to receiving systems suitable for receiving pulses of alternating current, such as may be characteristic of carrier telegraphy.

1 The receiving system to be described hereinafter is particularly adaptable for receiving alternating currents of especially low frequency. In accordance with the invention, pulses of such current are readily convertible into pulses of directcurrent, each pulse of direct current corresponding to its received pulse of alternating current.

One of the objects of this invention is to provide an improved arrangement for receiving signals such as are characteristic of carrier telegraphy.

Another of the objects of this invention is to provide an arrangement for receiving alternating current pulses and for converting these pulses into corresponding direct current ulses with small distortion in which the engths of the direct current pulses derived from the alternating current pulses correspond closely to the lengths of the direct current pulses which are employed at the sending end in producing said alternating current pulses.

Another of theobjects of this invention is to provide an arrangement for interconnecting a line circuit over which alternatin currentof some definite frequency, or o frequencies between the limits of a predetermined band, may flow,and a direct current relay so that the direct currentrelay may be continuously operated throughout the period during which current of the proper frequency or frequencies, is present in the line circuit.

And it is a further objectof this invention to interconnect a line circuit over which alternating current may flow, and a direct current relay through a pair of rectifying elements which respectively rectify theopposite halves of each alternating current cycle and provide the current necessary to operate the direct current relay} While this invention will be pointed out with particularity in the appended .claims, the invention itself, both as to its further objects and features, will be better under- 1929. Serial No. 348,499;

stood from the detailed description hereinafter following, when read in connection with the accompanying drawing, in which Figure 1 represents one embodiment of the invention employing a pair of rectifying elements for rectifying the current of a single source;

Fig. 2 represents both halves of an alternating current cycle disclosing the points at which the apparatus of Fig. 1 is particularly ceives such current as flows over line L freely transmitting these component frequencies lying between its predetermined limits and substantially suppressing all other frequencies. While this band filter may be of any well known type,- it is preferably of the type disclosed in the patent to G. A. Campbell, No. 1,227,113, dated May 22, 1917.

- The output of the filter is impressed upon a vacuum tube system, through a potentiometer P. This potentiometer is employed to control the magnitude of the voltage of the current to beimp-ressed upon the vacu tube system. e

The vacuum tube system includes a threeelectrode space discharge device V having grid, filament and plate electrodes. The filament electrode is heated to incandescence by the current derived from a battery B The grid electrode is connected to the filament electrode through the potentiometer P and a battery B the battery B biasing the grid electrode suitably negative with respect to the filament electrode. The plate electrode is connected to the filament electrode through a winding W and a battery B the battery B rendering the plate electrode at a suitably high positive potential with respect to the filament electrode. While this vacuum tube system is employed herein merely forthe purpose of amplifying the alternating current transmitted by filter F through potentiometer P, any other amplifying device or means may equally well be employed instead thereof within the scope of this invention. Moreover, if the current. transmitted by filter F and potentiometer P has consider,-

able energy, the vacuum tube system may,

perhaps, be omitted, in which event the otenti'ometer P will winding W A rectifying circuit is coupled to winding 1 through windings W and W This rectifying circuit includes the latter windbe terminated by .ings and the oppositely directed rectifiers D and D all arranged in series relation ship. The windings W and W are shunted by condensers C and C respectively. The point common to windings W and W and the point common to condensers C and C are tied together and both are grounded.

The direct current relay having three coupled windings, W W and W.-,, is designated by the reference character R. The

armature of this relay may vibrate between contacts 1 and 2 on either side thereof, and contact 1 may be closed in accordance with a. marking signal and contact 2 in accordance with a spacing signal.

A line which is suitable for transmitting direct current pulses characteristicof telegraphy is designated L This line is directly connected to the axis of rotation of the armature of relay R. The contacts 1 and 2, between which the armature of relayR may vibrate, are serially connected with resistances Z and Z and batteries B and B respectively, the point common to these hatteries being grounded. When the armature of relay R closes contact 1, current flows from battery 13,, through resistance Z over line L yet when this armature closes contact 2, current flows from battery B through resistance Z over line L.

A so-called kick transformer having windings W and W is placed between the rectifying circuit, above mentioned, and the direct current relay R. The primary winding of this transformer, i. e., W is connected serially between the point common to the rectifiers D and D and the winding W of relay R. The secondary winding of this transformer, 1. e., W is connected in a local manure armature nearer one pole of the relay than the other (not shown) or by any other means.

Winding W, of relay R is connected to ground through the resistance Z When no current flows over line L, or when current flows over line L having a frequency beyond the predetermined limits of filter F, the vacuum tube system will not be energized, the windings W and W will not be impressed with any current from winding the rectifiers D and D will rectify no current and will be otherwise ineffective, and thecondensers C and 0 will be discharged. Moreover, the continuous current from battery 13,; through the winding W, of relay R will cause the closure of contact 2 by the armature of relay R, and, moreover, current will flow from battery B over line L There will be substantially no current through either of the windings W or W of relay R.

When a pulse of alternating current of the proper frequency, orv in general, when current of any frequency or frequencies between predetermined limits of filter F are transmitted overline L this current will be freely transmitted by filter F, through potentiometer l, to the vacuum tube system. The potentiometer P nay be manipulated to adjust the voltage of the impressed current and, moreover, the vacuum tube system will amplify this current to any desired degree. Such current will be effective in energizing winding V Certain changes will be brought about in the condition of the rectifying .circuit and in the condition of the circuits associated with the windings of relay R, causing the armature of this relay to'move to its contact 1, and these will be considered in more detail in connection with Fig. 2 of the drawing which shows the positive and negative halves of a complete al ternating current cycle.

With the impression on line L of current of proper frequency, and therefore upon the vacuum tube system, it has already been suggested that the winding- W becomes eflee tively energized, and accordingly, windings W and W become similarly energized. During the positive half of the first alternating current cycle, inother words, between points 6 and d of Fig. 2, the voltage impressed upon these windings will rise from a zero value, as indicated by point Z) to a maximum value, indicated by point 0, and then decrease to the zero value, as indicated by point (X. Throughout the entire positive portion of the cycle, the impressed voltages are in a particular direction, as indicated by the arrows A On the other hand, with the impression of current of proper frequency upon the vacuum tube system, windings W and will hecome effectively energized, and during the negative half of each alternating current cycle, as between points (2 and f of Fig. 2, the voltage impressed upon these windings will again rise from zero, as indicated by point 61,

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' tion 0 to a maximum value, as indicated by point e,

and then decrease to zero, as indicated by point Throughout the entire negative porthe cycle, the impressed voltages are in the opposite direction, this direction being indicated by the arrows As the current impressed'upon windings W and l/V risesfrom the minimum value b to the maximum value 0, the voltages which are in the direction A cause current to flow through the rectifier D and the circuit through which this current flows may be traced from ground through winding W rectifier D winding W winding W resistance Z and ground. As the current increases in amplitude, soon the electromagnetic effect of winding W will exceed that of win'ding W causing the armature of relay Rto open contact 2, and move toward contact 1. Also, condenser 0 will become charged to the entire voltage of the impressed current. In fact, condenser C will become similarly charged, but the latter condenser will be ineffective in providing any current flow in rectifier D and therefore through winding W of relay R. It is shortly after the current magnitude departs from the point of zero amplitude b that the armature of relay R strikes contact 1. The length of the delay will depend, among other things, upon the strength of the biasing electromagnetic effect of winding W the reactance in the circuit of winding W ,'and the relative stiffness of the armature of relay R.

Between points 0 and d, the current impressed upon windings W and W will cause voltages in the same direction, i. e., A but these voltages will decrease and shortly become of zero or negligible magnitude. Throughout this portion of the cycle, current continues to flow through rectifier D and windings W and W and the armature of relay R' will remain closed against contact 1. However, condenser C Will begin to discharge through the circuit including rectifier D winding W winding'W resistance C and ground, and the discharge current will aid that derived from winding W in maintaining winding W sufficiently electromagnetic to overcome the biasing electromagnetic effect of winding W Therefore, during the balance of this half-cycle between points 0 and d, the armature of relay R will remain closed against contact 1.

Between that portion of the negative half of the cycle determined by points all and e, the current impressed on windings W and W will cause the production of voltages in the direction indicated by the arrows A and these voltages will rise from a zero or minimum value to a maximum value. The current impressed upon winding W will cause current flow through D in the circuit including winding W rectifier D winding W winding W resistance Z and ground. Windlng W Wlll receivedirect current which flows in the same direction as heretofore. Moreover, condensers C and C will become fully charged to the voltage of the impressed current, but it will be apparent thatcondenser C is practically ineffective in producing a current flow through detector D and winding W of relay R.

Between points e and f of the negative half of the alternating current cycle, the voltage of the current impressed upon windings ,VV and W will still be in the direction of arrow A but will be of decreasing order. This voltage will still be effective in producing a flow of current through detector D and windin N of relay R, However, condenser C Wi l discharge and assist winding W in maintaining a constant flow of current through detector D and winding W of relay R, the discharging circuit including condenser C rectifier D winding W winding W resistance Z and ground. Throughout the balance of this negative half of the cycle, the electromagnetic efiect of the winding W will be substantially greater than the biasing electromagnetic efl ect of winding W and consequently the armature of relay R will maintain contact 1 closed. It will be understood, moreover, that the armature of relay R will continue to remain closed against contact 1 throughout the remaining cycles of the alternating current pulse impressed upon Winding W It will be apparent also that the length of the delay or lag in the motion of the armature of relay R in departing from contact 1 after the completion of an alternating current pulse, will be practically the same as the length of the delay or lag of this armature in opening contact 2 and moving toward the contact 1 at the beginning of the ,tends to further couple winding W and winding W of relay When a current increasing at a rapid rate flows through winding W as at the beginning of a pulse, the

transformer will act to build up a substantial electromagnetic effect about winding W and therefore-the armature of relay R will move from contact 2 to contact 1 more promptly and more positively. On the other hand, at the termination of the alternating current or signaling pulse, this transformer will tend to set up a current in its secondary which will cause winding W to assist winding W inkretracting the armature of relay R. In effect then, the transformer causes the direct current relay R to become closely responsive to the envelope of the signals transmitted in the form of alternating current pulses.

stood, however, that the values of these frequencies are given merely for the sake of illustration, and other frequencies or bands of frequencies may equally well be employed within the scope and spirit of this invention. It will also be understood that these filters or the filter F of Fig. 1 may each be .replaced by any other device or means responsive to current of a definite frequency, or to currents having frequencies between predetermined limits, within the scope of this invention. It will be further understood that each of these filters may be omitted if desired,

or replaced by a tuned circuit arrangement of any well-known type which may include, for example, a pair 0 coupled induetances either or both of which are shunted by a condenser 0 variable capacity. In the latter event, one of these windings may be connected to line L, the other connected to the terminals of the potentiometer P, and the condenser of variable capacity shunting the latter winding, or if preferred, the former Winding.

In the arrangement of Fig. 3, the filament electrode of the vacuum tubes V and V are heated to. incandescence by a common battery B,, the interconnected circuit including battery 13,, resistance Z resistance Z the filament electrode of tube V resistance Z,, the filament electrode of tube V and ground. The How of current through resistances Z and Z causes a drop in potential across the respective terminals of these resistances, the drop in potential across Z biasing the grid electrode of tube V suitably negative with respect to filament electrode through the secondary of a transformer T and the drop in potential across Z being ample to suitably bias the grid electrode of tube V with respect to the filament of that tube through the secondary winding of transformer T In connection with the vacuum tube systems shown, it is to be noted that the battery B renders the plate electrodes of tubes V and V suitably positive with respect to the corresponding filament electrodes, through windings W and Wm, respectively.

The relays R and R control the transmission of directcurrent pulses over lines L and L respectively. It will be apparent that relays R and R operate in the manner already described. It is to be particularly noted that the biasing windings W and meters may, if desired, be shunted by re- .sistances Z and Z respectively.

It will be apparent that each vacuum tube system, each rectifying circuit, and all of the circuits associated with, each direct current relay in the arrangement of F ig. 3 operate in a manner substantially the same as already described hereinabove in connection with Fig. 1, and therefore this description need not be repeated. 7

It will be understood that each of the rectifying devices employed herein may be any dry disc rectifying device as, for example, a copper oxide rectifier which includes a metallic element, such as copper, in intimate contact with an oxide of the metallic element, such as copper oxide, or each may be a gas-filled tube of any well-known type,

or a two-element space discharge device which includes an incandescent filament electrode and a suitably positive plate electrode, or any other rectifying means.

While this invention has beendescribed in certain particular embodiments merely for the sake of illustration, it will be-understood that the general principles of this invention may be applied to other widely varied or ganizations 'without departin from the spirit of the invention and the scope of the appended claims.

What is claimed is:

1. In a signaling system, the combination of a source of current the frequency of which may vary within the limits of a band, a pair of copper oxide rectifiers connected in series with each other and coupled to said source,.

said rectifiers being oppositely directed and respectively rectifying opposite halves of each alternating current cycle, and a circuit including a direct current relay coupled to said'copper oxide rectifiers through which only unidirectional current may flow.

2. In a signaling system, the combination of a winding through which alternating current flows, a pair of oppositely directed contact rectifiers connected to said Winding in series relationship, each rectifier by-passing one-half the wave of each alternating current cycle, and a relay having a winding coupled to said rectifiers through which di rect current derived from said rectifiers continuously' flows.

3. In a signaling system, the combination of a series circuit including a first winding and a pair of oppositely directed contact rectifying elements, and a relay having a second winding connected in series between the midpoint of the first winding and the point common to said rectifying elements. V

4-. In a signaling system, the combination of a series circuit including a first winding and a pair of oppositely directed contact rectifying elements, a second winding connected in series between the point common to said rectifying elements and the midpoint of said first winding, and a pair of condensers of large capacity connected across each half of said first winding.

5. In a signaling system, the combination of two windings, two contact rectifiers, two condensers each of large capacity, and a direct current relay, said two windings being connected in series relationship with said rectifiers which are directed in opposition,

, each condenser shunting one of said WlIldformer for coupling the second and *celerate the ings, the winding of the direct current relay connecting the point common to said rectifiers with the point common to said first mentioned windings.

6. In a signaling system, the combination of a source of low frequency alternating current the frequency of which may vary between the limits of a band of predetermined width, means for rectifying both halves of each alternating current cycle, and a direct current relay through the winding of which the rectified current flows unidirectionally.

7. In a carrier telegraph system, means for periodically establishing a flows of alternating current in accordance with signals, and means responsive to said signals including a pair of rectifiers connected in opposition, one of the rectifiers rectifying the positive half of each alternating current cycle and the other of the rectifiers the negative half of each cycle, and a direct current relay through the winding of current flows unidirect-ionally, the direct current relay being energized only during the intervals when alternating current is being transmitted.

8. A system for receiving pulses of alternating current represent-ing telegraphic signals, including a rectifying current having a pair of oppositely directed rectifying elements which become alternately responsive at the beginning of a received alternating current pulse, a direct current relay having three windings the first of which is continuously energized, means whereby the second of the windin s may be energized only when the said recti ng elements become responsive to areceived pulse, and. a transthird of the direct current relay to acmotion of its armature at the beginning and at the end of each pulse.

9. In a telegraph. receiving system, the

windings combination of a direct current relay having three windings, a source of direct current potential, the first of the direct current windings being continuously energized with current from said source, a rectifying'circuit having a pair of oppositely directed rectifying elements which become alternately responsive to an impressed alternating current pulse and remain responsive throughout its impression, the second of' the windings of said direct current relay being energized with current derived from said rectifying circuit, and a transformer for coupling the second and third windings of said direct current relay to accelerate the motion of its armature at the beginning and at the end of'each pulse.

In testimony whereof, I have signed my name to this specification this 18th day of March, 1929.

FRED J. SINGER.

which the rectified 

